VAUCHERIA 



317 



but there are a number of species living in fresh water and some 

 on moist shaded soil. 



Vaucheria. Vaucheria (Fig. 272) is one form of the Sipho- 

 nales that is common in fresh water and on moist shaded soil. 

 The long filaments, usually much coarser than those of Spiro- 

 gyra and usually branched, interlace and form felt-like masses, 

 on which account Vaucheria is often called Green Felt. The 

 green or yellowish green felt- 

 like mats of the species grow- 

 ing on moist soil are common 

 in flowerpots and on and under 

 the benches in greenhouses. 

 Other species are common in 

 ponds and sluggish streams. 



Vaucheria forms zoospores 

 and heterogametes. In form- 

 ing a zoospore a portion of pro- 

 toplasm at the end of the fila- 

 ment is cut off from the rest 

 by a cross wall. This severed 

 mass of protoplasm escapes 

 from the filament as a multi- 

 nucleate and multiciliate zo- 

 ospore, large enough to be seen 

 with the naked eye. After 

 swimming about for a time 

 the zoospore comes to rest and 



FIG. 273. Botrydium granulatum. 

 At the left, the vegetative plant body, 

 showing the root-like projections be- 

 low and the balloon-like top above 



ground; at the right, a plant in which 

 zoospores have formed and are escap- 

 ing; between the enlarged plants, 

 plants about natural size. Drawn with 

 modifications from West and Wille. 



elongates into a new filament. 



Sexual reproduction shows 

 advancement in that the 

 gametes are borne in well-de- 

 fined sex organs, which are 



special structures for bearing sex cells. The oogonium, oval in 

 shape, bears one large egg, and the antheridium containing many 

 sperms is near it and is the end cell of a short curved branch. The 

 sperms escape, reach the egg through a special opening in the 

 oogonium, and one of them fertilizes the egg. The heavy-walled 

 oospore upon germination forms a new filament directly. 



There are, however, some Siphonales in which sexual reproduc- 

 tion is of a simpler type. For example, in Botrydium (Fig. 27 3) y 



